In the accumulation conveyor field it has long been desired to have a unit which can handle large, heavy articles and small, light articles on the same unit without interference and jamming between the various articles.
In prior accumulation conveyors where the force required to discontinue the conveyor drive when an article was stopped on the unit and to start the drive when the stopped article again moved has been provided by a sensor operated either by the weight or the movement of the article or both, troubles have arisen.
This is because small, light articles could not operate a clutch or the like of sufficiently heavy duty for the conveyance of heavy articles so that light and heavy articles could not be mixed on the same conveyor unless some extraneous power source such as compressed air or electricity was resorted to which required complicated mechanism, was expensive, required additional space and much maintenance. An example of a unit is disclosed by U.S. Pat. No. 3,225,893.
Efforts have been made to produce accumulation conveyors in which the power required to operate the clutch mechanisms to discontinue and then continue the movement of the conveyed articles is provided by the main conveyor drive, but such equipment to date has been complicated, expensive, and required frequent adjustments and general maintenance.
Examples of such prior art units are U.S. Pat. Nos. 3,219,172; 3,285,391; 3,156,345; 3,116,823; 3,164,246; 3,206,008, 4,108,303 and 3,232,415.